Blight & Woehler: First record of a Broad-billed Prion at Coronation Island 191
Marine Ornithology 36: 191 (2008) The known breeding distribution of Broad-billed Prions Pachyptila
vittata is restricted to Tristan da Cunha and Gough Islands in the South Atlantic Ocean and to offshore islands around New Zealand and the Snares and Chatham Islands, with the range at sea believed to extend to coastal South Africa in the South Atlantic Ocean and near-shore waters around New Zealand (Marchant & Higgins 1990).
The taxonomy of prions remains controversial, with most authors recognising up to six species, but varying numbers of subspecies.
The at-sea ranges of many Southern Ocean seabird species are still incompletely described, with relatively few surveys obtaining at-sea data for prions. Here, we report an observation of a Broad- billed Prion at the South Orkney Islands, approximately equidistant between the two known breeding distributions for this species.
On 9 December 2006, while surveying Adélie Penguin Pygoscelis adeliae colonies at Shingle Cove (60°39′S 45°20′W), Coronation Island, South Orkney Islands, we found the skull of a Broad-billed Prion on a coastal terrace below a steep scree bluff. Discarded wings and skeletal remains, primarily of Antarctic Prions P. desolata, were plentiful along the base of the bluffs behind the penguin colonies because of depredation by the five or more breeding pairs of Subantarctic Skuas Catharacta lonnbergi present. We were unable to collect the skull for formal identification because we had no collection permit, but we are confident of the identification because of the unique and unmistakable bill morphology of this species. For Broad-billed Prions, bill widths exceed 20 mm; this width contrasts with the much narrower bill (widths typically < 15 mm) of the Antarctic Prions present at this site. In addition, one of us (EJW) has had extensive experience handling and measuring Antarctic and Fulmar P. crassirostris Prions at Heard Island (Woehler 1991), and both authors have had considerable experience with observing all species of prions at sea.
This individual may have arrived at the South Orkney Islands as either a beach-washed carcass that was later scavenged by skuas,
FIRST RECORD OF A BROAD-BILLED PRION PACHYPTILA VITTATA AT CORONATION ISLAND, SOUTH ORKNEY ISLANDS
LOUISE K. BLIGHT1,2 & ERIC J. WOEHLER3
1Procellaria Research and Consulting, 944 Dunsmuir Road, Victoria, British Columbia, V9A 5C3, Canada
2Current address: Centre for Applied Conservation Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
(lkblight@interchange.ubc.ca)
3School of Zoology, University of Tasmania, Hobart, Tasmania, 7005, Australia Received 15 April 2008, accepted 2 August 2008
or as a bird blown out of its normal at-sea range by strong winds during poor weather. Alternatively, there may be low numbers of Broad-billed Prions breeding at poorly-surveyed sub-Antarctic colonies, such as the South Orkney Islands. Antarctic Prions are one of the most numerous seabird species in the Antarctic (Marchant &
Higgins 1990); they nest in the South Orkney Islands (Marchant &
Higgins 1990). It is possible that low numbers of breeding Broad- billed Prions have been overlooked amongst their congeners.
Although no sympatric breeding sites are known for the two species (Shirihai 2002) and the presence of this bird may have been an anomaly, our discovery may also represent an expansion in the recorded breeding range for Broad-billed Prions. Further surveys, particularly at night, would assist in determining whether breeding Broad-billed Prions are present in the South Orkney Islands.
ACKNOWLEDGEMENTS
Thanks to the expedition staff, officers and crew of the National Geographic M/V Endeavour for providing the logistics support that allowed us to survey this site. This paper is a contribution to the Antarctic Site Inventory, administered by Oceanites, Inc.
REFERENCES
MARCHANT, S. & HIGGINS, P.J. 1990. Handbook of Australian, New Zealand and Antarctic Birds. Vol. 1. Melbourne: Oxford University Press. 1400 pp.
SHIRIHAI, H. 2002. The complete guide to Antarctic wildlife:
birds and marine mammals of the Antarctic continent and the Southern Ocean. Princeton: Princeton University Press. 510 pp.
WOEHLER, E.J. 1991. Morphology of prions Pachyptila and diving petrels Pelecanoides at Heard Island. Marine Ornithology 19: 19–30.
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